How can I activate Shape in Tree tool?
I highly recommend using an improved version of Sapling that can be download from GitHub:
https://github.com/abpy/improved-sapling-tree-generator/archive/master.zip

Also, you can find this manual and presets useful too:
https://blenderartists.org/forum/showthread.php?395082-Blender-Sapling-Tree-Tutorial-%2528free-download%2529